Odpowiedź :
[tex] \frac{ \frac{1}{7} + \frac{4}{5} + x }{3} = \frac{1}{3} | \times 3 \\ \frac{1}{7} + \frac{4}{5} + x = 1 | \times 35 \\5 + 28 + 35x = 35 \\ 33 + 35x = 35 \\ 35x = 2 | \div 35 \\ x = \frac{2}{35} [/tex]
[tex] \boxed{ \boxed{Odp.C}}[/tex]